printf自定义实现中的错误

%pd ,其中p是要打印的字符数。

#include <stdio.h>
#include <ctype.h>
#include <stdarg.h>
#include <stdlib.h>

void print(char *, ...);
char *convert(unsigned int, int);
char *to_lower(unsigned int, int);
unsigned int count_digits(unsigned int);

int main()
{
    char str[12]="World";
    char c='A';
    int n = 5, x= 1011, y = 12, z = 5, t = 10;

    print("Hello s c |%s| |%c| 5 |%d| 5 some random %X %x %b %o words\n", str, c, n, x, y, z, t);
    print("%5d\n", y);

}

void print(char *format, ...)
{
    int num, precision = 0, nDigits, i, temp;
    char *num_deca;

    va_list lst;
    va_start(lst, format);

    while(*format != '\0')
    {
        if(*format != '%')
        {
            putchar(*format);
            format++;
            continue;
        }

        format++;

        if(isdigit(*format))
        {
            temp = atoi(format);
            precision = precision*10+temp;
            //precision = atoi(format);
            format++;
            continue;
        }
//      format++;

        switch(*format)
        {
            case 'c':
                putchar(va_arg(lst, int)); 
                break;
            case 'd':
                num = (va_arg(lst, int));
                //nDigits = count_digits(num);

                if(num > 0)
                {
                    num_deca = convert(num, 10);
                    nDigits = count_digits(num);
                    for(i = 0; i < (precision - nDigits); i++)
                    {
                        putchar(' ');
                    }
                    fputs(num_deca, stdout);

                   // fputs(convert(num,10), stdout);
                }
                else
                {
                    num = -num;
                    putchar('-');
                    fputs(convert(num,10), stdout);
                }
                break;
            case 's':
                fputs(va_arg(lst, char *), stdout);
                break;
            case 'X':
                num = va_arg(lst, int);
                fputs(convert(num,16), stdout);
                break;
            case 'x':
                num = va_arg(lst, int);
                fputs(to_lower(num,16), stdout);
                break;
            case 'b':
                num = va_arg(lst, int);
                fputs(convert(num,2), stdout);
                break;
            case 'o':
                num = va_arg(lst, int);
                fputs(convert(num,8), stdout);
                break;
        }

        format++;
    }

    va_end(lst);
}

char *convert(unsigned int num, int base) 
{ 
    static char Representation[]= "0123456789ABCDEF";
    static char buffer[50]; 
    char *ptr; 

    ptr = &buffer[49]; 
    *ptr = '\0'; 

    do 
    { 
        *--ptr = Representation[num%base]; 
        num /= base; 
    }while(num != 0); 

    return(ptr); 
}

char *to_lower(unsigned int num, int base) 
{
    static char Representation[]= "0123456789abcdef";
    static char buffer[50];
    char *ptr;

    ptr = &buffer[49];
    *ptr = '\0';

    do
    {
        *--ptr = Representation[num%base]; 
        num /= base; 
    }while(num != 0); 

    return(ptr); 
}

unsigned int count_digits(unsigned int n)
{
    unsigned int counter = 0;

    while(n != 0)
    {
        n = n/10;
        counter++;
    }

    return counter;
}

Output: Hello s c |World| |A| 5 |5| 5 some random 3F3 c 101 12 words
d

%5d% 应该是空格12(因为12只有2个数字)。我计算了参数的位数,并使用了一个for循环,该循环一直持续到精度和位数之间的差值,但是程序不再将d视为格式说明符的一部分,只打印字母“d”。知道为什么吗?